The present application is a continuation of International Application No. PCT/SE2004/001359, filed Sep. 21, 2004, which claims priority to SE 0302544-2, filed Sep. 24, 2003, both of which are hereby incorporated by reference.
The present invention relates to a method for regulation of the rotational speed of a clutch-independent power take-off arranged on a motor vehicle engine and driven by the vehicle engine. The invention also relates to a computer program or computer program product for said method.
In order to be able to handle the load on a truck efficiently, load-handling equipment is required. The most common examples of such equipment are tipping devices and cranes. Load changers, refuse handling units, rotary cement mixers, flushing units and air compressors for loading and discharging bulk loads are also commonly encountered.
In order to use the drive power of the vehicle engine to also drive the load handling equipment, a power take-off is required. The drive power from the power take-off can be transmitted either mechanically via a prop shaft or belts, or hydraulically by fitting a hydraulic pump to the power take-off.
Power take-offs are divided into clutch-independent and clutch-dependent power take-offs. The speed and power output of the clutch-independent power take-offs follow the vehicle engine irrespective of whether the vehicle is being driven or is stationary. Clutch-independent power take-offs are suitable for load handling equipment that is used when the vehicle is being driven, such as refuse handling units, cement mixers, cooling/freezer units and snow plows. The clutch-independent power take-offs can be fitted to the engine of the vehicle or fitted between the vehicle engine and transmission, but in front, that is to say on the engine side, of the plate clutch arranged between the engine and the transmission. EP 1147936 and GB 2272542 show examples of vehicles equipped with clutch-independent power take-offs.
Automatic transmissions of the automated stagegeared transmission type have become ever more common in heavier vehicles with the increasing development of microprocessor systems, making it possible, with a control computer and a number of control devices, such as servomotors, for example, to precisely regulate the engine speed, engagement and disengagement of an automated plate clutch between engine and transmission, and transmission internal clutch members in relation to one another, so that smooth gear changes are always achieved at the correct engine speed.
The advantage with this type of automatic transmission compared to a conventional automatic transmission made up of planetary gear trains and having a hydrodynamic torque converter on the inlet side lies partly in the fact that it is simpler and more robust and can be manufactured at substantially lower cost than the conventional automatic transmission, especially where used in heavy vehicles, and partly in that it affords greater efficiency, which means scope for reduced fuel consumption.
According to the prior art relating to vehicles equipped with said type of automated stagegeared transmission and coupling-independent power take-off, several operations are required in order to control both the output speed of the vehicle internal combustion engine, which determines the rotational speed of the power take-off, and an automated clutch (usually vehicles without clutch pedal).
There may even be restrictions on the driver performing certain maneuvers. When tipping a tipper body, for example, which is preferably done by means of a hydraulic arrangement connected to the clutch-independent power take-off, a relatively high speed on the output shaft of the power take-off is often required in order to perform more rapid maneuvers, i. e. to tip material speedily.
According to the prior art, this is most readily achieved by the driver depressing the accelerator pedal to the required degree. The transmission is then in neutral.
It is not uncommon, however, for the driver to also move the vehicle slightly forwards or backwards whilst the tipper body is being tipped. This would require the engagement of a gear in the gearbox, and for the vehicle to be driven forwards or backwards at low speed in a controlled manner, although this is not compatible, in this situation, with the high rotational speed of the engine. With the prior art, therefore, that is to say with a vehicle equipped with clutch-independent power take-off, automated stagegeared transmission and automated clutch, it is not possible to perform a maneuver as described above satisfactorily.
U.S. Pat. No. 5,522,778 shows an example of the prior art and a vehicle equipped with automated stagegeared transmission and power take-off.
There is therefore a need, in a vehicle equipped with clutch-independent power take-off and automated stagegeared transmission, to be able to drive the vehicle forwards or backwards independently of any simultaneous regulation of the rotational speed of the power take-off.
A method according to an aspect of the invention describes a method for regulating the rotational speed of a clutch-independent power take-off, the power take-off being driven by an engine arranged in a vehicle. The engine is connected to a transmission by way of an automated vehicle clutch. At least one control unit is arranged in the vehicle for controlling the vehicle clutch and the engine, the control unit controlling the rotational speed of the engine as a function of the position of a first control. The invention is characterized in that the rotational speed of the engine is regulated by way of a second control and the degree of engagement of the vehicle clutch is regulated by way of the first control when the power take-off is connected up and a drive position is selected by way of the gear selector.
An advantage of the method according to an aspect of the invention is that the driver of the vehicle can regulate the rotational speed of the power take-off whilst being able to drive the vehicle forwards or backwards. When a gear is selected by way of the gear lever and the power take-off is engaged, the driver of the vehicle can regulate the speed of the power take-off by way of the second control and can regulate the movement of the vehicle by way of the first control. The first control may take the form, for example, of the vehicle's throttle lever, such as an accelerator pedal arranged in the vehicle.
According to an aspect of the method according to the invention, the second control comprises a cruise control unit arranged in the vehicle. The normal function of the cruise control unit is to control the vehicle speed limiter. According to the invention, the cruise control unit assumes a further function when the power take-off is engaged and the gear lever is in a drive position. The advantage is that one control is used for multiple functions. In a second preferred embodiment of the method according to the invention, the second control comprises a control arranged in the vehicle for controlling/regulating equipment engaged to the power take-off. In a further embodiment of the method according to the invention, the rotational speed of the power take-off is regulated by way of a further separate control.
In a further aspect of the method according to the invention, the rotational speed of the engine and hence of the power take-off is automatically reduced when equipment coupled up to the power take-off approaches its limit position. The speed reduction may be successive from a point at which there is a certain calculated time remaining to the limit position.
An advantage of this aspect is that the impact and jerk that can occur when the equipment driven by the power take-off reaches a limit position is minimized. Wearing of the equipment and the drive unit is reduced.